The present invention relates to a method or system of controlling fluid flow. More particularly, the present invention relates to a nitrous oxide safety method or system which provides a safety control valve actuated by low-vacuum fluids to control the release of nitrous oxide therethrough.
Pneumatically-actuated on/off or control valves which open and close are known in the art. Such valves may include, for example, a piloted actuator which is opened and closed by a pneumatic, vacuum control fluid source which is connected to an input port on the valve. Movement of the piloted actuator is caused by a pressure differential created across the actuator by the control fluid.
Movement of the actuator may be used to perform a wide variety of functions. For example, movement of the actuator may control the flow of a second fluid source which is connected to a second input port on the valve. This type of valve acts as a monitor by responding to the vacuum input of the control fluid and then acts as a controller to actuate and/or control the flow of the second fluid through the valve.
Many applications require a pneumatically-actuated valve which is responsive to the input of a low vacuum pressure control fluid. As used herein, “low vacuum” is used to refer to vacuum strengths of 2-20 inches Hg, though performance within this range can be selected via design parameters. It should be understood that in a system with fixed conduit and orifice sizes, flow rate is proportional to vacuum strength levels.
In the dental field, the vacuum fluid is generated by an industrial vacuum system which services the individual devices within the dental operatory suites. For instance, these devices may include high volume oral evacuators, saliva ejectors, surgical suction and Nitrous Oxide (N2O) scavenging systems.
With a scavenging system, the mixture of gases, from excess input and exhalation, is suctioned from the mask by a vacuum source which is connected to and manually controlled by an on/off valve. These scavenged gases are safely exhausted outside of the operatory suite. NIOSH Alert 94-100 Controlling Exposure to Nitrous Oxide During Anesthetic Administration 1994 recommends a minimum flow rate of 45 liters per minute for vacuum scavenging systems.
In dental anesthesia/analgesia applications, it is critical that the vacuum source be activated and functioning properly at any time a supply of anesthesia/analgesia gas is delivered to the patient. If excess anesthesia/analgesia gas and exhalation gases from the patient are not scavenged by the vacuum source, a potentially hazardous condition builds up in the treatment room. In prior art anesthesia/analgesia configurations, the vacuum source is activated by a manual control valve which must be opened by an operator independently from the valve controlling the flow of anesthesia/analgesia gas.
A dangerous situation can exist where anesthesia/analgesia gas can be flowing without vacuum scavenging systems functioning. This could happen because of human error where the operator forgets to activate the vacuum scavenging system at the beginning of a procedure. Or, the operator could turn off the vacuum scavenging system and fail to properly turn off the anesthesia/analgesia gas at the end of a procedure. Also, it could occur due to a mechanical failure or overloading of the vacuum system, which is undetected by the operator, while anesthesia/analgesia gas is flowing.
Therefore, it would be particularly desirable to provide a system or method for nitrous oxide which provides a safety control valve actuated by low-vacuum fluids to control the release of nitrous oxide therethrough. Currently, there is no system in the prior art, used to safely control nitrous oxide flow proportional to the vacuum level.